1. Field of the Invention
The present invention relates to a network which provides an IPTV service by use of a passive optical network as an access network. The present invention more particularly relates to a system and a method in which a channel of an IPTV service is switched in a passive optical network.
2. Description of the Related Art
These days, a broadband service has been a telegraphic service remarkably important for an internet service provider and a terminal user. The passive optical network is regarded as a technology for the next generation that provides a broadband access.
An IPTV system changes an entertainment system of the terminal user from cable television to network television and from broadcasting television to interactive television. However, to provide an IPTV service in the existing IP network, a large number of technical supports such as a service quality technology and a safety technology are required. In addition, several problems have to be preferentially solved.
Among the problems, a channel switching time is one of important parameters of IPTV. In a conventional cable television system, the channel switching time is usually 100 milliseconds or less, and this can satisfy a demand of the terminal user during channel switching. However, in an IPTV system, a technology of encapsulation of an IP packet is used for image data and control information, and a TCP/IP system is a transmission system which derives the maximum capability. When the user needs to switch the channel, a time required for transmission of a channel switching request and reception of a request acknowledgment message from an image server is largely influenced by a network situation. Therefore, according to the existing technology, the channel cannot be switched at a high speed.
In U.S. Patent No. US2005/0265386A1, an image based on IP is transmitted using a WDM technology, and a PON packet format is corrected. However, the technology simply controls the switching of the channel by use of an IGMP protocol, and a problem that the channel be switched at a high speed is not solved. Since the passive optical network has a high optical transmission speed, a high-speed device including three layers is required in order to filter all IPTV signals through an IP layer. However, all IPTV terminals do not have a high-speed IPTV signal filter device.